Not everyone wants to vote strategically. Giving a candidate your vote is a form of endorsement. If I was a US citizen, I’d vote for Biden, and try to convince all my friends to do so, too. But I also understand the people who can’t bring themselves to vote for a guy supporting a genocide, no matter what the alternative is.
They’re basically saying “fuck it, if the system won’t give me a choice to vote against genocide, then I’m not participating in that system.”